In this episode, I’ll discuss the one formula that explains (almost) all inpatient medical emergencies.
Most pharmacists like formulas. Perhaps that’s why I think about the formula for oxygen delivery every time I respond to a rapid response call. Almost every time, figuring out the cause of the patient’s deterioration comes down to figuring out what the problem with oxygen delivery is.
Understanding and applying the formula for oxygen delivery will help you perform at a higher skill level when responding to inpatient medical emergencies.
The formula I’m referring to is:
Oxygen Delivery = stroke volume x heart rate x hemoglobin x %oxygen saturation
When oxygen delivery is impaired by one or more abnormalities on the right side of this equation, homeostatic mechanisms attempt to compensate to maintain oxygen delivery.
Before I talk about how to apply this formula during an inpatient medical emergency, I’ll review the 3 skill levels pharmacists can bring to code blue and rapid response team calls:
Level 1 I call “just being a pharmacist.” This is when you do regular pharmacist things like drawing up and labeling medications, and calculating doses. This work is valuable because it frees a nurse up to be hands-on with a patient.
Level 2 is helping to identify and reverse the cause of the patient’s deterioration. This includes listening to the bedside nurses description of what happened prior to the emergency and reviewing a patient’s medications, labs, and other clinical data to pinpoint the cause of deterioration.
Level 3 is predicting and preparing for the pharmacotherapy needs of the patient in advance, prior to the physician ordering medications for those needs. This involves having medications available and doses calculated for a patient you predicted would need to be intubated, or a vasopressor + IV pump + tubing ready for a patient you predicted would become hypotensive after intubation. Preparing for these needs in advance greatly reduces the usual lag time between a physician’s medication order and the implementation of that order to benefit the patient.
Understanding exactly how oxygen delivery is impaired helps with the identification of the cause of the patient’s deterioration and predicting and preparing for the pharmacotherapy needs of the patient. Here is a partial list:
Conditions that lower % oxygen saturation
Functional airway obstruction
Caused by a decreased level of consciousness whereby muscles relax and allow the tongue to obstruct the pharynx.
Treatments include:
- Airway maneuvers
- Antidote therapy
- Intubation
Mechanical airway obstruction
This could be caused by aspiration of foreign body, angioedema, bleeding, or stridor.
Treatments include:
- Anaphylaxis treatment
- Racemic epinephrine nebs
- Intubation (likely will be difficult) or surgical airway
Other causes of lower % oxygen saturation
- Pulmonary embolism
- Shunting
Causes of low hemoglobin
- Blood loss
- Coagulopathy
- Hemolysis (might be from meds!)
- Disseminated intravascular coagulation
Causes of decreased stroke volume
- Decreased contractility
- Distributive shock such as sepsis, pancreatitis, or anaphylaxis
- Myocardial infarction
- Acidosis
- Medications
Causes of decreased heart rate
- Any medication that blocks the sympathetic nervous system (metoprolol, clonidine)
- Hypoxia
- Vagal responses
By focusing on these causes of reduced oxygen delivery, you can reasonably predict when you will need medications to facilitate intubation, treat stridor, provide antidote therapy, raise blood pressure, treat coagulopathies.
At the beginning of this post, I noted that almost every inpatient medical emergency was explained by this formula. There is however at least one common and notable exception – hypoglycemia. So when you are in the middle of applying the oxygen delivery formula, don’t forget to check a fingerstick blood glucose!
For more on how to approach problems of oxygen delivery, get a copy of my book, A Pharmacist’s Guide to Inpatient Medical Emergencies, by going to clinicalpharmacybooks.com.
And no matter what skill level of code blue and rapid response you are at, the Hospital Pharmacy Academy has specific trainings to help you bring your emergency response skills to the next level. To learn more, go to pharmacyjoe.com/academy.
If you like this post, check out my book – A Pharmacist’s Guide to Inpatient Medical Emergencies: How to respond to code blue, rapid response calls, and other medical emergencies.
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